DATA      SEGMENT
MESS      DB 'TPCA INTERRUPT3!',0DH,0AH,'$'
DATA      ENDS
CODE      SEGMENT
            ASSUME CS:CODE,DS:DATA
START:    MOV      AX,CS
          MOV      DS,AX
          MOV      DX,OFFSET INT3
          MOV      AX,250BH
          INT      21H   
          IN       AL,21H
          AND      AL,0F7H
          OUT      21H,AL
          MOV      CX,10
          STI
LL:       JMP      LL
INT3:     MOV      AX,DATA
          MOV      DS,AX
          MOV      DX,OFFSET MESS 
          MOV      AH,09
          INT      21H
          MOV      AL,20H
          OUT      20H,AL
          LOOP     NEXT
          IN       AL,21H
          OR       AL,08H
          OUT      21H,AL
          STI
          MOV      AX,4C00H
          INT      21H
NEXT:     IRET
CODE      ENDS
          END      START